It only happened on a Win8.1 pro VM so far, I'm quite sure not a mouse problem, I tried a Microsoft mouse and a HP one, behave the same. Every thing was good when I run Paint.NET 4.0 alpha 3 on Windows 7 pro.
I wonder either it was a video performance problem of VM player 6.0 or Paint.NET 4.0 alpha 3 not match the VM, I found more issues in Win8.1 VM but not on the host Win7pro -- ahter select a area, any area, some noise lines flashing when I click the menu, and same thing happened on when I put mouse on the history window.
I want installed it on a physical Windows 8.1 box instead of VM, if the problem dispears I will not think it's a issue. I will not have computers for two weeks, will do and get it back next year.
Thanks for everybody and have great holidays.
Paint.NET is great.